Starflash, a clandestine superweapon, possessed the capability to unleash a massive discharge of tachyonic and lightspeed energy upon a star, triggering a significantly amplified return surge. Approximately five millennia prior to the Battle of Yavin, it was delivered to the Chiss Ascendancy, remaining unused until the Final Assault on Csilla centuries afterward. When the enemy fleet had massed into close proximity, the weapon was activated, resulting in the destruction of the fleet, Starflash itself, and the twenty Chiss operators. A second Starflash, designated simply as the item, was acquired thousands of years later and remained in the possession of the Stybla family by the conclusion of the Clone Wars.
An unidentified alien species conceived Starflash more than five thousand years before the Battle of Yavin. The Stybla family obtained it during a period of Chiss exploration circa 5000 BBY. Given its immense destructive power, it was concealed within the Bastion (the precursor to the Universal Analysis Group), with the intention of never deploying it.
Centuries later, the Chiss Ascendancy found itself under attack by an unidentified enemy. This foe conquered every planet belonging to the Ascendancy except for Csilla. It was at this critical juncture that the Stybla Patriarch recalled the existence of Starflash. Twenty Mitth warriors, including the four sons of Mitth'omo'rossodo, volunteered to operate the weapon. It was installed aboard a vessel that positioned itself at the center of the enemy fleet, and then fired at Csilla's sun. The subsequent energy release obliterated the fleet and Starflash, although fragments of the device survived. This event caused Csilla's star to noticeably dim over the following decades, eventually compelling the Chiss to relocate underground.
The Patriarchs collectively decided to suppress the truth surrounding the Final Assault on Csilla and the existence of Starflash. Upon the selection of new Patriarchs, their Senior Aides would apprise them of this ancient Chiss history. Many centuries hence, the Stybla family acquired another Starflash and secreted it away within the vaults of the Universal Analysis Group on Sposia. Knowledge of this second device was confined to the Patriarch and Senior Aide of the family, and occasionally a select few others. Around the time of the Clone Wars, Supreme Admiral Ja'fosk and Supreme General Ba'kif possessed this knowledge. Then-Senior Commander Mitth'raw'nuruodo and Syndic Mitth'ras'safis were also informed after they recovered a piece of it with Senior Aide Stybla'ppin'cykok.
The debut mention of Starflash occurred in the 2021 novel titled Thrawn Ascendancy: Greater Good, the second book in the Star Wars: The Ascendancy Trilogy authored by Timothy Zahn.